This invention relates to printing composite images containing visible and invisible postage and address information that can contain large amounts of information. The composite image provides high information density in a highly reliable and visually pleasing form. This invention addresses the problem of obscuration of IBI modules by printed text intended for visual human reading, such as the address.
Postage evidencing information, including IBI images, is a significant feature of the Information-Based Indicia Program (IBIP) proposed by the United States Postal Service (USPS) as a distributed trusted system. The IBIP open systems for applying postage in addition to using a postage meter to mechanically print indicia on mailpieces. The IBIP requires printing high density, two-dimensional (2-D) bar codes, such as PDF417 bar codes, on mailpieces. The requirements for printing a PDF417 2-D bar code are set forth in The “Uniform Symbology Specification”. The Postal Service expects the IBIP to provide cost-effective assurance of postage payment for each mailpiece processed. IBI images comprise certain human readable information and two-dimensional (2-D) bar code information, which can contain such assurance. There is a need for a high-density image format that includes both human readable and bar code information with high readability.
The USPS has published specifications for the IBIP as PERFORMANCE CRITERIA FOR INFORMATION BASED INDICIA PROGRAM, dated Feb. 23, 2000, and referred to herein as the “IBIP specifications”. The IBIP includes interfacing user (customer), postal and vendor infrastructures, which are the system elements of the program. The term “postage evidencing information” is meant to include IBI images meeting the current IBIP specifications as well as alternative formats. The IBIP specifications require a minimum bar code read rate of 99.5% and place the responsibility on each IBIP vendor to meet this requirement.
The IBIP specifications permit large format IBI images, e.g., 2-D bar codes, but there are several practical limits to the use of images that overlap conventional address information. For example, if conventional address information overlaps with the IBI image, the IBI image could lose reliability and fall outside of Specifications.
The need for high resolution has posed significant technical challenges. Current systems are challenged to provide a suitable combination of convenience, acceptable appearance and high readability at high information densities. In U.S. Provisional Patent Application No. 60/392,996, to Michael J. Critelli, et al., there is described a system which enables printing large amounts of information on a mailpiece without causing the mailpiece to become unsightly due to the presence of too much printing in a small space. The system employs invisible ink or lightly colored ink for printing at least a portion of the bar code portions of the information. This system has the advantage that attempts to maximize print information in an invisible 2-D bar code will not affect the human readable portion. Including redundancy in the invisible 2-D bar code improves readability.
When using invisible, fluorescent ink for printing the 2-D bar code, the bar code will not obscure the human readable printed information, but the human readable printed information can obscure the bar code. Overlap of the 2-D bar code and the printed conventional human readable address information can diminish the readability of the 2-D bar code or other information to the extent that even error correction codes cannot obtain the required read rates. Typically, fluorescent inks irradiate in the red or infrared range when excited by ultraviolet light. But, because black and other dark visible inks tend to quench fluorescence, any overprinting of dark ink and a fluorescent ink can cause obscuration to the point of diminishing or destroying readability. Black ink will quench fluorescence even if the fluorescent ink is printed over the black ink. FIG. 6 shows obscured address information.
There remains a need for a method that provides machine-readable IBI images containing both large format 2-D bar code information in invisible or light colored luminescent ink, along with conventionally printed address and postage information to provide increased read rates and the provision of high information density without obscuring any one component. It would be desirable in this context to provide especially enhanced readability with a high contrast of the fluorescent image in a format that enabled improved read rates in the presence of obscured information.